14 . COLEOPTERA OF NORTH AMERICA. 



internally, the outer lobe biarticulate and vvith equal joints; palpi 

 ratlier stout, the terminal joint nearly as long as the second, 

 gradually broader to tip and obtuse. Thorax transverse, a seta 

 at point of greatest width, another in front of the hind angles. 

 Bases of thorax and elytra in close apposition, scutellum indis- 

 tinct. Elytra not margined at base, moderately inflexed at the 

 sides, the margin acute and entire. Anterior coxal cavities closed 

 behind, prosternuni slightly prolonged and partly covering the 

 declivous and flat mesosternum. Femora moderately stout, the 

 anterior scarcely thicker. Anterior tibiiB obliquely grooved and 

 eniarginate near the apex, both spurs terminal. Middle tibias 

 ciliate externally. Posterior coxaj separated by a rather broad 

 triangular process of the abdomen. Tarsi moderate, first joint 

 longer than either of the three following, fourth not eniarginate. 



The first joint of the anterior tarsus of the male is rather 

 broadly dilated and with the second is densely spong}^ pubescent 

 beneath. 



The metasternal side pieces of which no mention is made above 

 are sometimes simple, that is, with all trace of suture between 

 the episternura and epimeron obliterated, or the suture may be 

 more or less distinct and the side pieces consequently double. 



This tribe contains but a single Californian species {Metrms 

 contractus Esch.), of singular form, found under stones in forests. 

 It is a very distinct type, the affinities of which are not easy to 

 define. The posterior coxa9 being separated, a relationship seems 

 to be indicated with the Promecognathini and Cychrini, espe- 

 cially with the latter by the more widely inflexed sides of the 

 elytra, but it differs widely from either by the structure of the 

 anterior tibite. The pi'esence of a setigerous puncture on the 

 mandible is a very curious addition to the other characters, and 

 is in nearly if not quite all other cases associated with riparial 

 habits, which cannot be said of Metrius. 



The genus Metrius is placed by Schaum in the preceding tribe, 

 which he defines as having the mesosternum carinate in front. 

 Such is not the case with this genus, which it therefore becomes 

 necessary to remove. It cannot certainly enter any other tribe 

 known to us, and Dr. LeConte was therefore compelled to sepa- 

 rate it as distinct. 



